3.0 Poor Mileage

[tecboy99]

Hey all, recently I noticed that the OBC is reporting around 13MPG combined. I was shocked when I saw this because I thought I normally got somewhere in the 18-19 range. First thing I did was check tire pressure, They were all fine. Then I fired up INPA and looked at my adaption values. Everything looks fine. What about that "tv probe heating before kat bank 1" and 2. They are locked at 99.31. That means they are trying to richen the mixture, right? Let me know what you guys think.

[StephenVA]

I will have to do some research but I thought that reading was the heating elements in the O2 Sensors actually working to operational temps.

When you look at cross counts on the O2 sensors what do you see? Rich/Lean fluctuations at idle and 2500 RPM. Are they stuck at rich or lean? (Pre cat)

[Green Dragon]

It's all in that right foot of yours! Making that exhaust sing. J/K I have'nt played with INPA yet, but I agree with what stephen said. It's showing the Pre O2 Heating. Very interesting data you have access to. Does resetting adaptations help since you made some fairly drastic changes? Sometimes these ecu's will freak out a bit.

I'm wondering about the fuel quality. It suffers in winter due to blend, for sure, but that's quite a dive. Do you feel like the torque band has moved since installing headers? Maybe you are having to dig a little deeper on acceleration? I noticed this between open headers and no exhaust. Once the exhaust was hooked up, I had more torque down low. All kinds of power mid range and up high, just the low end felt anemic. Once everything was hooked up, it felt great. As far as mileage tests goes, I didn't really have a chance to test it but once. I did a small 150 mile round trip and it did very well without really trying. It was summer. I couldn't keep my foot out of it none the less.

I'm really interested. Pm me if you need. You just may need to put some miles on it and let it settle out.

[g300d]

What are your coolant operating temps?

BMW forces these engines to run hot (ave 96 or so) for better fuel economy by electronically actuating the thermostat via DME signal.

These thermostats more commonly fail open and cause cooler operating temps, with correspondingly worse gas mileage.

Just one thing more thing to check out.

[Helihover]

Ya engine temp would help with the readings.

You have a tune? Or just the 02 delete?

[tecboy99]

Thanks for the ideas everyone. As far as coolant operating temperatures goes, The coolant temp is always in the midrange. I've never gotten a tstat stuck open code so I think we can rule that out. Green Dragon, I'm sure that my foot has been slightly heavier. But, it has been in the past, and hasn't gone this low. Interesting thing happened. My adaptions were freaking out after I installed my headers. I also had codes stored for the missing post cat sensors. I figured out that when you do the Euro 2 flash, the post cat 02's and air pump need to be unplugged. Otherwise, the system thinks it's equipped. I simply reflashed the DME and reset adaptions. Which fixed the error codes and the values jumping all over the place. I didn't really notice any big change in the low end torque after the mufflers were connected. Maybe I need those 3.64 diffs For now, I'm going to remove my Thule ski rack, top up the tires and get some BP 93 since I need gas anyways. I'll let you know how it goes. Also, I your inbox is full.

[Green Dragon]

Ahhh crap! In box has now been cleaned. Thanks man.

[lovbyts]

Curious what you found out or if your still having the same problem.

[tecboy99]

Originally Posted by lovbyts

Curious what you found out or if your still having the same problem.

I bumped up the tire pressure to 35 all around and let the adaptions settle down. I get about 18.5MPG combined with mostly city driving. Always in a spirited manner, of course.